Presensitized foil for planographic and offset printing



United States Patent 3,235,382 PRESENMTHZED Ffllit, FQR PLANOGRAPHIC AND OFFSET PRINTING Wilhelm Neugebauer, Wieshaden-Biebrich, Hartmut Steppan, Wiesbaden-Dotzheim, and August Rebenstock, Wiesbaden-Biebrich, Germany, assignors to Kalle Ahticngesellschaft, Wiesbaden-Biebrich, Germany, a corporation of Germany No Drawing. Filed Apr. 1, 1963, Ser. No. 269,758 Claims priority, application Germany, Apr. 3, 1962, K 46,366 30 Claims. (Cl. 96-33) Recently, processes have been developed for the preparation of printing plates for planographic and offset printing in which light-sensitive diazo compounds of high molecular weight are employed. Light-sensitive coatings containing such materials are applied to lithographic sup ports of many different types, e.g. metal foils or plates and paper.

Various suggestions have been made with a view to improving the shelf life of such light-sensitive materials. Thus, it has been proposed to include in the light-sensitive layer a substance which renders the light-sensitive diazo compounds ditficultly soluble, or to use the diazo compounds of high molecular Weight in conjunction with other diazo compounds, or to convert these diazo compounds into the corresponding diazo sulfonates or diazoamino compounds. However, such diazo sulfonates and diazoamino compounds possess considerably less lightsensitivity and do not accept greasy printing ink as readily as the parent diazonium salts.

It has also been proposed to sensitize printing foils by means of condensation products of diazonium salts with active carbonyl compounds. The light-sensitivity of these substances is satisfactory, but printing foils containing these substances have only a brief shelf life so they are unsuitable for many purposes.

The present invention provides a copying material for use in planographic and offset printing which comprises a non-metallic support having a light-sensitive coating which contains a product of condensation, in a strongly acid medium, of a substituted or unsubstituted diphenylamine- 4-diazonium salt with a compound containing a reactive carbonyl group and which also contains an excess of a strong acid, other than phosphoric acid, in an amount of 1 to 100 equivalent weights of acid per mole of diazonium groups.

Due to the combination of the three necessary features, viz, a non-metallic support, the use as the light-sensitive material of the above-mentioned condensation product, and the excess of acid, the light-sensitive copying material has outstanding shelf life, and gives long printing runs.

Excess of acid means acid present in free form, i.e. not bound to diazonium groups or to any other organic or inorganic base.

The excess of acid in the light-sensitive layer should amount to at least one equivalent Weight of acid per mole of diazonium groups. An excess greater than three equivalent weights of acid is generally to be preferred. With inonobasic acids, the equivalent weight is the molar weight of the acid. In the case of polybasic acids which are active as strong acids in more than one stage of dissociation, e.g. sulfuric acid, the equivalent weight is to be considered as that submultiple of the molecular weight which corresponds to the number of stages of strongly acid dissociationin the case of sulfuric acid, therefore, it is half the molecular weight. In the case of polybasic acids, which are strong acids in the first stage of dissociation only, the equivalent Weight is the molar weight,

The following are examples of suitable acids: sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid,

perchloric acid, hydrofluoboric acid, alkyl phosphonic acids, organic sulfonic acids, e.g. toluene sulfonic acid, methane sulfonic acid and naphthalene-1,5-disulfonic acid, amidosulfonic acids, selenic acid, arsenic acid, vinyl phosphonic acid and hexafluorophosphoric acid (HPF Slightly volatile acids may be used with advantage, e-.g. sulfuric acid, arsenic acid and aromatic sulfonic acids. The use of sulfuric acid is particularly advantageous, first because of the low price of this acid and second because the good solubility of polyfunctional diazonium salts in water, and in mixtures of water with organic solvents, is not adversely affected by the presence of sulfuric acid. Also, particularly favorable results are obtained with this acid.

The light-sensitive substances which may be used are polyfunctional diazonium salts obtained by the condensation of substituted or unsubstituted diphenylamine-4-diazonium salts with reactive carbonyl compounds in an acid medium, eg in one of the following acids or in mixtures thereof: sulfuric acid, phosphoric acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, benzene sulfonic acid, toluene sulfonic acid, methane sulfonic acid, ethane sulfonic acid, chloromethyl phosphonic acid, selenic acid, arsenic acid, vinyl phosphonic acid and hexafiuorophosphoric acid (HPF Substituents which may be linked to the phenyl nuclei of the diphenylamine-4-diazonium compounds are, e.g.: alkyl and alkoxy groups, particularly such having 1 to 6 carbon atoms, further halides and the following groups:

. Carbonamide, CONH Cyan, CN

Acyl, -COR (R=alkyl or aryl) Alkoxy sulfonyl, SO R (R=alkyl) Aryloxy sulfonyl, SO R (R=aryl) Acylamino, NHCOR (R=alkyl or aryl) Alkylamino, NHR and NR (R=alkyl) Arylarnino, -NHR and NR (R=aryl) Sulfo, S-O H Examples of such substit-uents which may be linked to the phenyl nuclei of the diphenyldiazonium groups are: methyl, ethyl, propyl, butyl, isobutyl, methoxy, ethoxy, fluorine, chlorine, brorn, iodine, ethoxy carbonyl, phenoxy carbonyl, acetyl, methoxy sulfonyl, ethoxy sulfonyl, acetamino, rnethylamino, ethylamino, dimethylamino, diethylamino, methylethylamino, phenylamino, benzylamino, methylbenzylamino, and ethylbenzylarnino.

The diphenylamine-4-diazonium salts used to make the condensation products may be derived, for example, from the following amines:

4-amino-diphenylarnine, 4-amino-3-methoxy-diphenylamine, 4-amino-Z-methoxy-diphenylamine, 4'-amino-2- methoxy-diphenylamine, 4'-amino 4 methoxydiphenylamine, 4-amino-3-methyl-diphenylamine, 4-amino-3-ethyldiphenylarnine, 4-amino 3 methyldiphenylamine, 4'- amino-4-rnethyldiphenylamine, 4-amino-3- -ethoxydiphenylamine, 4-arnino 3 hexyloxydiphenylamine, 4'-ainino-6- methoxy-3-methyldiphenylamine, 4 amino--methoxy-3- methyldiphenylamine, 4' amino-3,3'-dimethyl diphenylamine, 3'-chloro-4-aminodiphenylamine, 4-amino-2,5-diethoxydiphenylamine, 4'-amino-4-n-butoxydiphenylamine and 4'-amino-4,3-dimethoxydiphenylamine.

The diphenylamine-4-diazonium compounds may be reacted with the reactive carbonyl compound in the form of their salts with a strong acid, eg. as salts of sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, alkylphosphonic acid or arylphosphonic acid, trifluoroacetic acid, hydrofluoboric acid, methane sulfonic acid, toluene sulfonic acid and other aliphatic or aromatic sulfonic acids, amidosulfonic acid, selenic acid, hexafiuophosphoric acid or perchloric acid. Alternatively, the diazonium compounds may also be used in the form of their double salts with metal salts for the reaction with the reactive carbonyl compounds.

Aliphatic, aromatic, mixed aliphatic/ aromatic and heterocyclic aldehydes and ketones may be used as the active carbonyl compound. The aldehyde or ketone may also contain unsaturated linkages. Preferred aliphatic compounds are those containing 1 to 11 carbon atoms in the molecule and preferred aromatic and mixed aliphatic/ aromatic compounds are those containing 7 to 13 carbon atoms in the molecule. The best results are generally obtained with condensation products in which formaldehyde is the sole or at least one of the active carbonyl compounds reacted with the diazonium salt. However, condensation products with other active carbonyl compounds, e.g. acetaldehyde, isobutyraldehyde, benzaldehyde, benzaldehyde-3-sulfonic acid, chloral, acetone, butanone, di-isobutyl ketone, acetophenone, benzophenone, benzil, pyroracemic acid, cinnamaldehyde, naphthalene-l-aldehyde, phenanthreno-quinone-sulfonic acid, pyridine-3-aldehyde and quinoline-4-aldehyde, or mixtures of such compounds, can also be used.

The polyfunctional diazonium salts can be salts of the most widely differing acids, e.g. fluorides, chlorides, borates, trifluoracetates, arsenates, salts of organic sulfonic acids, salts of alkyl phosphonic acids and salts of aryl phosphonic acids.

The polyfunctional diazonium salts can also be associated with metal salts, i.e. in the form of double salts, e.g. with metal halides. In fact, all double salts of the aforementioned polyfunctional diazonium salts which have sufficient solubility in at least one of the solvents commonly used for the preparation of coating solutions can be employed. Thus, the double salts may be the precipitates which are obtained from solutions of such diazonium salts by the addition of zinc chloride, cadmium chloride, zinc bromide, cadmium bromide, cobaltous chloride or stannic chloride. For example, the commercially available Zinc chloride salt of the condensation product of diphenylamine-4-diazonium sulfate and formaldehyde, prepared by condensation in sulfuric acid, can be used and this can be applied to the support after the addition of sulfuric acid. A similar light-sensitive coating is obtained if diphenylamine-4-diazonium sulfate is condensed in sulfuric acid with formaldehyde, under the conditions used for the preparation of the commercially available product, and the condensation mixture, with an addition of zinc chloride, and a possible further addition of other acid, is diluted with solvent and used for the coating.

The nature of the support determines to some extent which of the products condensed in the different acids can be used with greatest success. For example, with a paper support as described in US. Patent 2,778,735, practically all of the condensation products listed above can be used with equal success, while with a support of superficially saponified cellulose acetate foil, condensates prepared in sulfuric acid are generally most suitable.

The paper support described in the US. patent consists of a coated paper provided with a calendered layer which layer consists essentially of a carboxy methyl hydroxy ethyl cellulose adhesive which was rendered insoluble and in which the ratio of carboxymethyl groups to hydroxy ethyl groups is in the range of 0.3 to 1 and the degree of substitution of the anhydro glucose units exceeds 0.8, and a larger quantity of nonaqueous pigment, viz. blanc fixe and/ or titanium dioxide.

To prepare copying material according to the invention, the intended light-sensitive diazonium salt is dissolved in a suitable solvent, which may be water, an organic solvent, or a mixture of water with an organic solvent together with an excess of one or more of the strong acids and the solution is applied to the support in the usual manner, e.g. by swabbing or on a whirler; the coating is then dried.

The concentration of the coating solution depends upon the nature of the support and upon the method used for coating. Generally, good coatings are obtained when the coating solution contains from 0.05 to 10 percent, by weight, preferably 0.2 to 5 percent, of diazo compound. Higher concentrations than 10 percent by weight also give satisfactory results.

The quantity of strong acid applied to the support per mole of diazonium groups also is dependent primarily on the nature of the support. It is further dependent upon the type of diazo compound and on the concentration of the diazo compound in the coating solution. On the paper support described in U.S. Patent 2,778,735, for example, if sulfuric acid is used and the concentration of diazo compound in the coating solution is 1 percent, 1 to 100, preferably 3 to 50, equivalent weights of acid are used per mole of diazonium groups, i.e. 0.5 to 50, preferably 1.5 to 25 moles. Larger quantities of acid may be added. In the case where the support is a superficially saponified cellulose acetate foil, less than this quantity of acid is ordinarily used.

The light-sensitive layer may be prepared by simply diluting with a suitable solvent a crude condensate produced from the substituted or unsubstituted diphenylamine-4-diazonium salt and the reactive carbonyl compound, in particular formaldehyde, in sulfuric acid or another of the acids listed above, further acid being added if necessary, the resulting solution being then applied to the support and dried.

The suitability of such crude condensates is surprising because condensation products of diphenylamine-4-diazonium salts and formaldehyde exhibit a tendency, when stored at room temperature, to decompose slowly with evolution of gas and, in the course of a few hours or days, to continue condensating to such an extent as to form products which are insoluble or difficultly soluble in water and still less soluble in organic solvents.

It has now been found that crude condensates can be prepared in sulfuric acid which do not, under normal conditions, continue condensing to form insoluble products and which have excellent shelf life. Crude condensates having these favorable properties are obtained when the diphenylamine-4-diazonium salt (which is preferably very pure) is condensed with formaldehyde in 30 to 90 percent by weight sulfuric acid, preferably 55 to percent by weight, and in the case of surfuric acid having a concentration of over 60 percent, only 1 to 4 moles, preferably 1.5 to 2.5 moles, of sulfuric acid are used per mole of diazonium groups and the condensation is effected with slight heating, e.g. to 40 C. Thus, a crude condensate prepared from 1 mole of formaldehyde 2 moles of sulfuric acid, in the form of 70 percent sulfuric acid, and 1 mole of pure diphenylamine-4-diazonium sulfate has an excellent shelf life. Even after storage for 50 days at 40 to 45 C., it still forms a clear solution in water. In sulfuric acid of lower concentration than 60 percent by weight, condensation is slower, prolonged heating is necessary and a larger quantity of acid is preferably used, i.e. about 3 to 15 moles per mole of diazo compound. If 1.5 to 2.5 moles of acid per mole of diazo compound are used, condensation can be effected in sulfuric acid of a higher concentration than 85 percent. In such a case, however, the condensation reaction can easily become too vigourous because in such a viscous mixture the temperature easily rises locally to quite a high level despite cooling and this can result in the formation of water-insoluble components.

Even with sulfuric acid of higher concentration than 85 percent, crude condensates with very good shelf life can be produced if sufficient sulfuric acid is used for the mixture to be readily stirrable during condensation so that effective heat exchange with the cooling liquid is possible. In such a case, the condensation is effected at the lowest possible temperature, e.g. between 0 and (2., and, after condensation is complete, the reaction material is diluted with water or dilute sulfuric acid until the final concentration of sulfuric acid is below 85 percent by weight, preferably between 60 and 70 percent. Crude condensates obtained in this way are also suitable for use in the copying material according to the invention.

It is of advantage, though not essential, in the preparation of the crude condensate to use 1 mole of formaldehyde, or an equivalent of one of its polymers, per mole of the diazo compound. However, suitable products are also obtained when less or more formaldehyde is added, per mole of diazo compound. Crude condensates which contain several moles of formaldehyde per mole of diazo compound exhibit a tendency to continue condensing in storage to produce products of less solubility.

The crude condensates in sulfuric acid are brown oils which have good storage and transporting qualities. They have particularly good shelf life when prepared from diphenylamine-4-diazonium salts which are unsubstituted or substituted by alkyl groups. The crude condensates are in general, readily soluble in water and in mixtures of water with organic solvents.

Good shelf life is not, however, an essential condition for the successful use of the crude condensates because the elimination of precipitates of solid condensation products is in itself an advantage. In the case of crude condensates which can be stored for only a short time, condensation is effected immediately before coating and is interrupted as soon as optimum condensation is attained, the crude condensate being immediately diluted with a suitable solvent to the required concentration for coating. After the addition, in appropriate cases, of more strong acid, preferably sulfuric acid, the solution is ready for use.

The coating may also include conventional additives, such for example as film-formers and antioxidants.

The copying material is converted into a printing plate in the usual way, i.e. the copying material is exposed to light under a negative and then wiped over with water, or with an aqueous gum arabic solution which may contain an organic solvent, e.g. methylene glycol, or with an aqueous solution of a salt, e.g. disodium phosphate or ammonium chloride, and is then inked up with greasy ink. A positive printing plate is obtained which gives a long run of satisfactory prints. To improve the length of run, the printing image can be reinforced with lacquers, e.g. those described in US. Patent 2,754,279. It is sometimes advantageous to remove the diazo compound from the support which after development still may adhere to the printing plate in the non-printing areas. This may be effected by applying to the plate a hydrophilic colloid layer, exposing the whole plate to light and then washing with water or an aqueous solution.

In the following examples parts by weight are in grams and parts by volume are in milliliters.

Example 1 A paper support, prepared as described in U.S. Patent 2,778,725, is coated by swabbing With a solution containing 2.6 parts by weight of a crude condensate prepared as described below and 2.3 parts by weight of concentrated sulfuric acid in 100 parts by volume of water. The copying material is then dried in a current of hot air.

The preparation of the crude condensate is as follows: 158 parts by weight of diphenylamine-4-diazonium sulfate (93 percent solution in water) are intimately mixed with parts by weight of paraformaldehyde. Over a period of 15 minutes this mixture is introduced into 151 parts by weight of 65% sulfuric acid and the suspension is heated, with stirring, for 8 hours to 40 C. A yellowbrown, highly viscous oil is formed which has excellent shelf life. This crude condensate dissolves in water without leaving any residue after storage for days at a temperature of 40 to 45 C.

Instead of the condensation product just described, the following crude condensate can also be used. 100.6 parts by Weight of diphenylamine-4-diazoniun1 sulfate (97 percent solution in water) and 10 parts by weight of paraformaldehyde are intimately mixed and the mixture is introduced, at a temperature between 20 and 25 C., into 408 parts by weight of percent sulfuric acid. The mixture is heated for 6 hours to 40 C. The crude condensate keeps well at room temperature. To prepare the coating solution, 6.3 parts by weight of the crude condensate are dissolved in 100 parts by volume of water.

A copying material of good quality is also obtained when the following crude condensate, which also has good shelf life, is used: 30.3 parts by weight of dip-henylamine-4-diazonium sulfate (96 percent solution in water) are mixed with 3 parts by weight of paraformaldehyde and the mixture is introduced into 40.8 parts by weight of 96.4 percent sulfuric acid, which has been cooled to 0 C., with such rapidity that the temperature does not rise above 10 C. The mixture is stirred for one hour at this temperature and then diluted, dropwise with good stirring, with 11 parts by weight of water taking care that the temperature does not rise above 12 C. The coating solution in this case contains 3 parts by weight of the crude condensate and 3 parts by weight of concentrated sulfuric acid in 100 parts by volume of water.

The copying material so obtained is exposed, for example through a negative, for two minutes to an l8-amp carbon arc lamp at a distance of approximately 60 cm. It may be developed by treatment with water or aqueous gum arabic solution. The resulting positive printing plate is inked up or run in a printing machine with greasy ink. A large number of excellent prints can be produced. The length of printing run obtainable can be further extended if the printing image is reinforced with lacquer, e.g., the emulsion lacquer described in US. Patent 2,754,279. When protected from light and stored under dry conditions, the copying material keeps well.

Example 2 A coating solution is prepared as follows: 2.4 parts by weight of a crude condensate, the preparation of which is described below, and 3.6 parts by weight of concentrated sulfuric acid are dissolved in 100 parts by volume of Water. The copying material prepared by the application of this coating solution to the paper support used in Example 1 has very good storage qualities.

To prepare the crude condensate, a mixture of 35 parts by weight of 3-methoxy-diphenylamine-4-diazonium sulfate (92 percent solution in water) with 3 parts by weight of paraformaldehyde is introduced, with initial cooling, into 21 parts by weight of percent sulfuric acid and condensation is continued for 6 hours at 40 C.

A copying material of good storageability and good performance is also obtained if for the coating a solution containing 2.1 parts by weight of a crude condensate, the preparation of which is described below, and 3.2 parts by weight of concentrated sulfuric acid in 100 parts by volume of Water is used. To prepare the crude condensate, a mixture of 32.4 parts by weight of 4-rnethoxydiphenylamine-4-diazonium sulfate and 3 parts by weight of paraformaldehyde is introduced, with initial cooling, into 18.4 parts by weight of percent sulfuric acid. Condensation is effected by heating for 6 hours to 30 to 40 C.

The copying material is converted into a printing plate as described in Example 1.

Example 3 The paper support used in Example 1 is coated with a solution containing 2 parts by weight of a crude condensate, the preparation of which is described below, and 3.2 parts by weight of concentrated sulfuric acid in parts by volume of water. The preparation of the copying material is in other respects as in Example 1.

To prepare the crude condensate, a mixture of 46 parts by weight of 4-methyl-diphenylamine-4-diazonium sulfate and 4.95 parts by weight of paraformaldehyde is introduced into 27.5 parts by weight of 80 percent sulfuric acid and heated for 21 hours to a temperature of 40 C. for the condensation reaction.

A copying material which keeps well and can be processed as described in Example 1 is obtained.

Example 4 The paper support used in Example 1 is coated on a plate whirler with a coating solution containing 1.16 parts by weight of a polyfunctional diazonium chloride, the preparation of which is described below, and 6.1 parts by weight of paratoluene sulfonic acid in 100 parts by volume of glycol monomethyl ether.

A copying material with good storageability is obtained which can be converted into a high performance printing plate as described in Example 1.

To prepare the diazo compound, 23.1 parts by weight of diphenylamine-4-diazonium chloride are mixed with 3 parts by weight of paraformaldehyde and introduced into 50 parts by volume of concentrated hydrochloric acid. Condensation is etfected for 7 hours at 50 C. and the mixture is concentrated in portions by evaporation in vacuo at temperatures not exceeding 65 C. The resulting polyfunctional diazonium chloride contains 0.5 to 1 mole of hydrochloric acid per mole of diazo compound.

Instead of the foregoing coating solution, a solution can be successfully used for coating the support which contains 1.16 parts by weight of the same diazo compound together with 5.5 parts by weight of 82 percent arsenic acid or parts by weight of 66 percent hydrobromic acid in 100 parts by volume of glycol monomethyl ether.

Good results are also obtained if a coating solution is used which contains 1.16 parts by weight of the same diazo compound and 12.5 parts by weight of 31 percent hydrofluoboric acid in 100 parts by volume of glycol monomethyl ether.

Example 5 The paper support used in Example 1 is coated with a solution containing 2 parts by weight of a crude condensate, the preparation of which is described below, and 5 parts by weight of concentrated sulfuric acid in 100 parts by volume of water. The processing of the copying material is as in Example 1.

To prepare the crude condensate, an intimate mixture of 122 parts by weight of 3-methoxy-diphenylamine-4- diazonium chloride (86 percent solution in water) and 12 parts by weight of paraformaldehyde is introduced into 84.5 parts by weight of 65 percent hydrobromic acid and condensed for 14 hours at a temperature of 40 C.

Instead of this crude condensate, a crude condensate prepared in an analogous manner but with 2 to 3 moles of concentrated hydrochloric acid per mole of diazo compound can be used with equal success.

Example 6 The paper support used in Example 1 is coated with a solution containing 1 part by weight of a crude condensate, the preparation of which is described below and 2 parts by weight of concentrated sulfuric acid in 100 parts by volume of glycol monomethyl ether.

To prepare the crude condensate, 30.3 parts by weight of diphenylamine-4-diazonium sulfate (96.4 percent solution in water) are introduced into 100 parts by weight of 90 percent sulfuric acid, 6.4 parts by weight of acetone are then slowly introduced at C. The product is used after being allowed to stand for 24 hours.

After exposure under a negative master, the copying material can be developed by wiping over with water or aqueous gum arabic solution and the printing plate can be inked up with greasy ink.

Example 7 The paper support of Example 1 is coated with a filtered solution of 1 part by weight of a condensation product in the form of a tin chloride double salt (87 percent), the preparation of which is described below, and 4.7 parts by weight of concentrated sulfuric acid in parts by volume of water, and the coating is dried in a hot air current. A presensitized printing foil which may be stored for a long time is obtained.

To prepare the condensation product, a mixture of 15.4 parts by weight of diphenylamine-4-diazonium chloride and 2 parts by weight of paraformaldehyde are introduced into 33 parts by weight of commercially available concentrated hydrochloric acid and condensation is effected for 7 hours at 50 C.. The condensation mixture is diluted with water, the tin chloride double salt of the condensation product is precipitated by the addition of a solution of tin tetrachloride containing hydrochloric acid, and the precipitate is separated and dried.

The resulting printing foil is exposed under a negative master and wiped over with water or an aqueous gum arabic solution. A printing plate is obtained which gives a long run of excellent prints.

A copying material of good storage qualities is also obtained if a coating solution is used containing 1 part by weight of the condensation product in the form of a cadmium chloride double salt, which is described below, and 4.3 parts by weight of concentrated sulfuric acid in 100 parts, by volume, of water. This reproduction material also yields high-performance printing plates.

To prepare the diazonium cadmium chloride double salt, 25 parts by weight of diphenylamine-4-diazonium sulfate are introduced into 68 parts by volume of 78 percent sulfuric acid. 2.6 parts by weight of paraformaldehyde are then added, with stirring, over a period of 3 hours. Stirring is continued for 2 hours at room temperature, and for 2 hours at 40 C., and the mixture is allowed to stand overnight. The crude condensate is stirred into 600 parts by volume of isopropanol, to remove most of the sulfuric acid, and the precipitate is filtered off and dissolved in parts by volume of water. The double salt, precipitated by the addition of hydrochloric acid and excess concentrated cadmium chloride solution, is filtered otf, washed thoroughly with dilute hydrochloric acid, and dried.

Example 8 The paper support of Example 1 is coated with a solution containing 1.6 parts by weight of a condensation product (88 percent) in the form of a zinc chloride double salt, the preparation of which is described below, and 5 parts by weight of concentrated sulfuric acid in 100 parts by volume of water. It is then dried.

Instead of the 5 parts by weight of concentrated sulfuric acid used above, 6 parts by weight of 82 percent arsenic acid or of a mixture of equivalent quantities of concentrated sulfuric acid and 82 percent arsenic acid can be used with equal success.

To prepare the diazonium salt, 22.5 parts by weight of 3-methoxy-diphenylamine-4-diazonium sulfate are introduced, at room temperature, with stirring, over a period of one hour, into a solution of 2.05 parts by weight of paraformaldehyde in 43.5 parts by volume of 78 percent sulfuric acid. Stirring is continued for one hour at room temperature, for another hour at 40 C., and for a further 1.5 hours at room temperature. Most of the sulfuric acid is removed by stirring the condensation mixture into isopropanol. The resulting precipitate is separated off and washed in water and the zinc chloride double salt 'is precipitated from the solution by the addition of excess concentrated zinc chloride solution and hydrochloric acid. After filtering, the precipitate is washed with dilute hydrochloric acid, again washed with isopropanol and then dried.

The copying material is exposed, for example under a negative master, wiped over with water to develop it and inked up with greasy ink. In this way a positive printing plate is obtained which yields long runs.

A copying material of good quality is also obtained if, instead of the above compound, a condensation product is used, in the form of its zinc chloride double salt, which was analogously prepared from 4-methoxy-diphenylamine- 4-diazonium sulfate.

Example 9 A paper support, as used in Example 1, is coated with a solution containing 1.8 parts by weight of a cobalt chloride double salt of the diazo compound described below and 14 parts by weight of p-toluene sulfonic acid in 100 parts by volume of water, and is dried.

To prepare the diazo compound, a mixture of 46 parts by weight of 4-methyl-diphenylamine-4'-diazonium sulfate and 4.95 parts by weight of paraformaldehyde is introduced into 27.5 parts by weight of 80 percent sulfuric acid and condensed for 21 hours at 40 C. 10 parts by weight of the crude condensate are dissolved in a mixture of 100 parts by volume of isopropanol and 10 parts by volume of concentrated hydrochloric acid. A solution of parts by weight of cobalt chloride (hexahydrate) in 100 parts by volume of isopropanol is then introduced. The double salt which precipitates is filtered off, washed with isopropanol and dried. The use of the material as a printing plate may be as in Example 1.

Example The paper support of Example 1 is coated on a whirler with a solution containing 0.7 part by weight of a condensate in the form of the zinc chloride double salt, the preparation of which is described below, and 3 parts by weight of concentrated sulfuric acid in 100 parts by volume of glycol monomethyl ether, and is then dried in a hot air current. A presensitized printing foil with good storage qualities is obtained. It can be further converted into a printing plate as described in Example 1.

The diazo compound is prepared as follows: 30.3 parts by weight of diphenylamine-4-diazonium sulfate (96.4 percent solution in water) are introduced into 100 parts by weight of 90 percent sulfuric acid and then 6.4 parts by weight of acetone are introduced dropwise at C. After being allowed to stand for 24 hours at room temperature, the condensate is dissolved in water and clarified with charcoal. The double salt of the diazo compound is then precipitated out of the aqueous solution by the addition of aqueous zinc chloride solution in known manner, filtered off, and dried.

Examples 11 and 12 A paper support of the kind described in Example 1 is coated with a solution containing 7.5 parts by weight of the raw condensate described below in 100 parts by volume of water, and the support is then dried.

For the preparation of the raw condensate, 2.1 parts by weight of pyridine-B-aldehyde are dissolved in 21.8 parts by Weight of 90 percent sulfuric acid, 5.9 parts by weight of diphenylamine-4-diazonium sulfate are introduced into the solution, and the reaction mixture is then left standing for 12 hours at room temperature.

After exposure of the plate under a master, development is effected with water. The printing plate is then inked with greasy ink. It yields a large number of flawless prints.

Equally good results are obtained, if, for making the coating solution, a raw condensate is used which was prepared analogously to that described above, using, however, 3.2 parts by weight of quinoline-4-aldehyde instead of the pyridine-3-aldehyde mentioned above.

Example 13 A paper support similar to that used in Example 1 is coated with a solution containing 16 parts by weight of the raw condensate described below, dissolved in a mixture of 60 parts by volume of ethyleneglycol monomethylether and 40 parts by volume of dimethylformamide.

For the preparation of the raw condensate, 4.1 parts by weight of the sodium salt of benzaldehyde-3-sulfonic acid and 5.9 parts by weight of diphenylamine-4-diazonium sulfate are introduced into 21.8 parts by weight of percent sulfuric acid, and the reaction mixture is kept standing for 12 hours at room temperature.

Development of the plate, which has been exposed under a master, can be effected with water.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A presensitized printing plate which comprises a non-metallic support having a light-sensitive layer thereon, the latter comprising a condensation product, condensed in a strongly acid medium, of a diphenylamine-4- diazonium salt with a compound containing a reactive carbonyl group, and an excess of a strong acid selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, perchloric acid, hydrofluoboric acid, alkyl phosphonic acids, organic sulfonic acids, amidosulfonic acids, selenic acid, arsenic acid, vinylphosphonic acid, and hexafluorophosphoric acid, in a quantity of at least one equivalent weight of acid per mole of diazonium groups.

2. A presensitize d printing plate according to claim 1 in which the condensation product is used in the form of a crude condensate, in acid, of the diazonium salt and the compound containing the reactive carbonyl group.

3. A presensitized printing plate according to claim 1 in which the condensation product is used in the form of :a crude condensate, in sulfuric acid, of the diazonium salt and the compound containing the reactive carbonyl group.

4. A presensitized printing plate according to claims 3 in which the condensation product is condensed in sulfuric acid of more than 60 percent concentration, 1 to 4 moles of acid being used per mole of diazonium groups.

5. A presensitized printing plate according to claim 1 in which the condensation product is in the form of a double salt with a metal salt.

6. A presensitized printing plate according to claim 1 in which the support is paper.

7. A presensitized printing plate according to claim 1 in which the diazonium salt is diphenylamine-4-diazonium sulfate.

A presensitized printing plate according to claim 1 in which the diazonium salt is S-methoxy-diphenylamine- 4-diazonium sulfate.

9. A presensitized printing plate according to claim 1 in which the diazonium salt is 4-methyl-diphenylamine- 4-diazonium sulfate.

10. A presensitized printing plate according to claim 1 in which the diazonium salt is 4-methoxy-diphenylamine- 4-diazonium sulfate.

11. A presensitized printing plate according to claim 1 in which the diazonium salt is diphenylamine-4-diazonium chloride.

12. A presentsitized printing plate according toclaim 1 in which the diazonium salt is 3-methoxy-diphenylamine- 4-diazonium chloride.

13. A presensitized printing plate according to claim 1 in which the compound containing a reactive carbonyl group is paraformaldehyde.

14. A presensitized printing plate according to claim 1 in which the compound containing a reactive carbonyl group is acetone.

15. A process for developing a printing plate which comprises exposing a coated non-metallic base material to light under a master and developing the resulting image, the coating comprising a condensation product, condensed in a strongly acid medium, of a diphenylamine- 4-diazonium salt with a compound containing a reactive carbonyl group, and an excess of a strong acid selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, perchloric acid, hydrofiuoboric acid, alkyl phosphonic acids, organic sulfonic acids, amidosulfonic acids, selenic acid, arsenic acid, vinylphosphonic acid, and hexafluorophosphoric acid, in a quantity of at least one equivalent weight of acid per mole of diazonium groups.

16. A process according to claim in which the condensation product is used in the form of a crude condensate, in acid, of the diazonium salt and the compound containing the reactive carbonyl group.

17. A process according to claim 15 in which the condensation product is used in the form of a crude condensate, in sulfuric acid, of the diazonium salt and the compound containing the reactive carbonyl group.

18. A process according to claim 15 in which the condensation product is condensed in sulfuric acid of more than 60 percent concentration, 1 to 4 moles of acid being used per mole of diazonium groups.

19. A process according to claim 15 in which the condensation product is in the form of a double salt with a metal salt.

20. A process according to claim 15 in which the support is paper.

21. A process according to claim 15 in which the diazonium salt is diphenylamine-4-diazonium sulfate.

22. A process according to claim 15 in which the diazonium salt is 3-methoxy-diphenylamine-4-diazonium sulfate.

23. A process according to claim 15 in which the diazonium salt is 4-methyl-diphenylamine-4'-diazonium sulfate.

24. A process according to claim 15 in which the diazonium salt is 4-methoXy-diphenylarnine-4-diazoniurn sulfate.

25. A process according to claim 15 in which the diazonium salt is diphenylamine-44iiazonium chloride.

26. A process according to claim 15 in which the diazonium salt is 3-methoxy-diphenylamine-4-diazonium chloride.

27. A process according to claim 15 in which the compound containing a reactive carbonyl group is paraformaldehyde.

28. A process to claim 15 in which the compound containing a reactive carbonyl group is acetone.

29. A presensitized printing plate according to claim 1 in which at least one of the phenyl nuclei of the diazonium salt carries a substituent selected from the group consisting of alkyl, alkoxy, halide, carboxy, carboxylic ester, carbonamide, cyan, acyl, alkoxy sulfonyl, aryioxy sulfonyl, acylamino, alkylamino, arylamino, sulfo.

30. Coating solution for making a sensitized printing plate comprising a solvent and dissolved in said solvent a condensation product condensed in a strongly acid medium, of a diphenylamine-4-diazonium salt with a compound containing a reactive carbonyl group, and an excess of a strong acid selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, perchloric acid, hydrofluoboric acid, alkyl phosphonic acids, organic sulfonic acids, amidosulfonic acids, selenic acid, arsenic acid, vinylphosphonic acid, and hexafiuorophosphoric acid, in a quantity of at least one equivalent weight of acid per mole of diazonium groups.

References Cited by the Examiner UNITED STATES PATENTS 2,063,631 12/1936 Schmidt et a1. 9691 X 2,100,063 11/1937 Zahn 96-91 X 2,679,498 5/1954 Seven et a1. 96-33 X FOREIGN PATENTS 698,040 10/ 1953 Great Britain.

OTHER REFERENCES Handbook of Chemistry and Physics, Chemical Rubber Publ. Co., Cleveland, Ohio, 38th ed., 1956-1957, page 1621.

Pauling: General Chemistry, Freeman and Co., San Francisco, Calif., 1947, page 396.

NORMAN G. TORCHIN, Primary Examiner. 

1. A PRESENSITIZED PRINTING PLATE WHICH COMPRISES A NON-METALLIC SUPPORT HAVING A LIGHT-SENSITIVE LAYER THEREON, THE LATTER COMPRISING A CONDENSATION PRODUCT, CONDENSED IN A STRONGLY ACID MEDIUM, OF A DIPHENYLAMINE-4DIAZONIUM SALT WITH A COMPOUND CONTAINING A REACTIVE CARBONYL GROUP, AND AN EXCESS OF A STRONG ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID, HYDROCHLORIC ACID, HYDROBROMIC ACID, NITRIC ACID, PERCHLORIC ACID, HYDROFLUOBORIC ACID, ALKYL PHOSPHONIC ACIDS, ORGANIC SULFONIC ACIDS, AMIDOSULFONIC ACIDS, SELENIC ACID, ARSENIC ACID, VINYLPHOSPHONIC ACID, AND HEXAFLUOROPHOSPHORIC ACID, IN A QUANTITY OF AT LEAST ONE EQUIVALENT WEIGHT OF ACID PER MOLE OF DIAZONIUM GROUPS.
 15. A PROCESS FOR DEVELOPING A PRINTING PLATE WHICH COMPRISES EXPOSING A COATED NON-METALLIC BASE MATERIAL TO LIGHT UNDER A MASTER AND DEVELOPING THE RESULTING IMAGE, THE COATING COMPRISING A CONDENSATION PRODUCT, CONDENSED IN A STRONGLY ACID MEDIUM, OF A DIPHENYLAMINE4-DIAZONIUM SALT WITH A COMPOUND CONTAINING A REACTIVE CARBONYL GROUP, AND AN EXCESS OF A STRONG ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID, HYDROCHLORIC ACID, HYDROBROMIC ACID, NITRIC ACID, PERCHLORIC ACID, HYDROFLUOBORIC ACID, ALKYL PHOSPHONIC ACIDS, ORGANIC SULFONIC ACIDS, AMIDOSULFONIC ACIDS, SELENIC ACID, ARSENIC ACID, VINYLPHOSPHONIC ACID, AND HEXAFLUOROPHOSPHORIC ACID, IN A QUANTITY OF AT LEAST ONE EQUIVALENT WEIGHT OF ACID PER MOLE OF DIAZONIUM GROUPS. 